Blackwell

A trap net survey was conducted on Blackwell Lake on July 11-12, 2022 by Index of Biological Integrity (IBI) Program Staff. Nine trap nets were set along the shoreline in locations that encompassed multiple habitat types. Bluegill comprised a majority of the trap net catch by number. The number of Bluegill sampled per net was above the 25% quartile and below the 50% quartile for similar Lake Class 34 lakes and the average length was 5.3 inches, with 14% over seven inches. Bluegill, Northern Pike, and Yellow Bullhead comprised a majority of the trap net catch by biomass. The fish data collected in this trap net survey were combined with data from an August 2020 gill net survey and July 2020 survey of nearshore fishes to describe the fish community and provide a Fish-based IBI (FIBI) score. The FIBI uses fish community data to measure a lake's health, and the types of fish species present can help identify any stressors that may be negatively affecting the lake environment. In Minnesota lakes, certain fish species cannot survive without clean water and a healthy habitat (e.g. Blacknose Shiner, Iowa Darter, and Smallmouth Bass), while other species are tolerant of degraded conditions (e.g. Black Bullhead and Common Carp). The FIBI score, composed of several fish community diversity and composition metrics, indicates the overall health of a lake by comparing it to what is expected for a healthy lake. For additional information on the FIBI, search for "lake index of biological integrity" on the mndnr.gov website. Results from this survey provide evidence that the fish community in Blackwell Lake is in good health as indicated by an FIBI score above the impairment threshold for aquatic life use determined for similar lakes. Data from this survey will contribute biological information about the health of the fish community to the Long Prairie River Watershed assessment process in coordination with MN Pollution Control Agency.

A targeted survey was completed in the spring of 2022 on Blackwell Lake to assess the Bluegill and Black Crappie populations. A special regulation that reduced the daily sunfish limit from 20 down to 10 was also implemented in the spring of 2022. The goal of this new regulation is to maintain or increase the average size of Bluegill. This survey will be used to help evaluate effects of the regulation on the Bluegill population. Bluegill catch rates were high, but only 13% of Bluegill were preferred size (> 8 inches). Growth rates of Bluegill in Blackwell Lake are slow and 7-year-old Bluegill averaged 7 inches in length. The largest Bluegill observed in the survey was just over 9 inches. Black Crappie catch rates were high and a variety of sizes were observed in the survey. Approximately 29% of the fish were greater than 10 inches in length. Black Crappie growth rates are slow; average length of age 4 fish was under 9 inches. The largest Black Crappie in the sample was over 11 inches and the oldest crappie was 8 years old. Quality fishing opportunities exist for multiple species in Blackwell Lake. Anglers are encouraged to practice selective harvest to help sustain the quality of the fishery. Selective harvest encourages the release of larger fish while promoting harvest of more abundant smaller fish. Releasing medium to large fish can help restore and maintain fish community balance, as well as increase opportunities to catch large fish. Zebra mussels were documented in Blackwell Lake in 2021, but no other invasive species have been documented. Anglers are reminded to drain boats and equipment prior to moving between bodies of water to minimize the risk of transferring aquatic invasive species to this or other lakes.

Blackwell Lake is a 307-acre lake located nine miles southwest of Alexandria, near the town of Holmes City. There is a public access located on the southeast shoreline off of Country Lane SW. Two concrete launches with docks are now available. An additional launch and parking were added in 2020. The northern basin has a maximum depth of 42.0 feet, while the southern bays tend to be shallow and vegetated. The average depth is 10.0 feet. Water quality and clarity (9.5 feet during this survey) are good. This is the result of an abundant and diverse aquatic plant community. Aquatic vegetation also provides valuable spawning habitat and cover for many fish species. Submergent vegetation can be seasonally dense in shallow areas of the lake. Emergent vegetation is common in the southern area of the lake. This type of habitat is characteristic of "bass-panfish" lakes and the fish community in Blackwell Lake is reflective of this. A standard fisheries survey was completed during summer 2020 to provide updated information on the fish community of Blackwell Lake. Standard survey components typically include spring electrofishing, gill nets, and trap nets. However, due to safety concerns during the COVID-19 pandemic, gill nets were the only component used in 2020. Historically, Bluegill have been very abundant and small in this basin. Bluegill were still abundant in the 2020 survey, but are now at sizes that would be of interest to anglers. Average and maximum lengths were 6.9 and 8.9 inches, respectively. Black Crappie abundance was moderate, but comparable to recent surveys. Catches in August tend to be conservative due to the tendency of crappie to move offshore and into deeper water during summer months. Average and maximum lengths were 9.3 and 12.4 inches, respectively. Anglers can expect to encounter good numbers of Largemouth Bass. Average and maximum lengths were 13.4 and 17.8 inches, respectively. Northern Pike are abundant but tend to be small. Average length was just 19.6 inches but a 33.3-inch pike was sampled. Anglers are encouraged to harvest small pike. New Northern Pike zone regulations were implement in 2018 to increase pike size structure. Blackwell Lake is in the North-central Zone, where all pike 22 to 26 inches must be released. Anglers can keep 10 pike but not more than two can be longer than 26 inches. Northern Pike taken by spearing follow the same rules except one pike may be between 22 and 26 inches, or two larger than 26 inches. For more information see: https://www.dnr.state.mn.us/pike/index.html. Blackwell Lake is not managed for Walleye but a population persists at a low density in response to limited natural reproduction or migration from connected waters. Four Walleye were sampled ranging in length from 7.0 to 19.5 inches. Yellow Bullhead were abundant and at sizes that may be of interest to some anglers. Additional species sampled include Pumpkinseed and White Sucker. The next standard fisheries survey is tentatively scheduled for 2026. Blackwell Lake is not a designated infested water. Aquatic invasive species (AIS) are moved from infested to non-infested waters by anglers, boaters, and lake shore owners and can negatively affect lakes and fish populations. To avoid spreading AIS, lake users are required to remove all aquatic plants or animals from their watercraft and drain water from their boat before leaving the access. For more information regarding aquatic invasive species see the following: https://www.dnr.state.mn.us/invasives/ais/index.html

Based on Minnesota DNR survey data, anglers target Largemouth Bass, Northern Pike, Hybrid Sunfish, Yellow Perch, and Green Sunfish in Blackwell. See the full species list above for catch rates, size structure, and quality scores.

Minnesota DNR records list public access for Blackwell. Check the DNR LakeFinder page for the launch type and directions before you go.

Blackwell has a maximum depth of 42 feet and a mean depth of 10 feet, per Minnesota DNR data.

The most recent Minnesota DNR survey data for the main sport fish in Blackwell is from 2022.

Yes — Blackwell has confirmed zebra mussel. Clean, drain, and dry your equipment to avoid spreading invasives to other waters.